Three-dimensional terminal angle constraint finite-time dual-layer guidance law with autopilot dynamics

Considering the problem of intercepting a target at desired terminal angles in the three-dimensional (3D) space, this paper proposes a finite-time dual-layer guidance law with consideration of the second-order autopilot dynamics. The proposed guidance law owns a cascaded structure, which is divided into an outer system and an inner system. To achieve the finite-time convergence, the outer and inner controllers are developed based on the nonsingular terminal sliding mode control. With the aid of the command filter, which can compute the first and the second derivatives of the virtual signal simultaneously, the design procedure of the fourth-order guidance system is simplified into two steps. Moreover, extended state observers are used to estimate the unknown target maneuver and the acceleration derivative of the missile, which facilitates the real implementation. Simulation results verify the performance of the proposed guidance law.